function menu() {

    var page1 = document.getElementById("page1");
    var page2 = document.getElementById("page2");
    var page3 = document.getElementById("page3");
    var menuOne = document.getElementById("menuOne");
    var menuTwo = document.getElementById("menuTwo");
    var menuThree = document.getElementById("menuThree");
    var page_1 = document.getElementById("page_1");
    var page_2 = document.getElementById("page_2");
    var page_3 = document.getElementById("page_3");


    page1.onclick = function() {
        menuOne.style.display = "block";
        menuTwo.style.display = "none";
        menuThree.style.display = "none";
    }
    page2.onclick = function() {
        menuOne.style.display = "none";
        menuTwo.style.display = "block";
        menuThree.style.display = "none";
    }
    page3.onclick = function() {
        menuOne.style.display = "none";
        menuTwo.style.display = "none";
        menuThree.style.display = "block";
    }


    page_1.onclick = function() {
        menuOne.style.display = "block";
        menuTwo.style.display = "none";
        menuThree.style.display = "none";
    }
    page_2.onclick = function() {
        menuOne.style.display = "none";
        menuTwo.style.display = "block";
        menuThree.style.display = "none";
    }
    page_3.onclick = function() {
        menuOne.style.display = "none";
        menuTwo.style.display = "none";
        menuThree.style.display = "block";
    }

}